The present invention relates generally to electronic theft detection devices and, more particularly, to the attachment of theft-detection devices to articles of merchandise to increase the tamper resistance of the device and to reduce the vulnerability cf the device to unauthorized removal.
Various devices and systems have been developed in the retail marketing industry for deterring shoplifters. In the retail clothing business, electronic theft detection systems are in common use. These systems typically employ a `target` device, known in the art as a `wafer`, that is attached to an article of clothing using a releasable attachment system. Radio frequency interrogators are used to generate interrogation fields in or adjacent the shopping area exits. The target wafers generally include a resonant circuit which responds in some predetermined manner to the interrogation field to reliably detect an attempted unauthorized removal of the protected goods.
One such target wafer and attachment system is disclosed in U.S. Pat. No. 4,187,509, issued on Feb. 5, 1980 to A. Weiner for "Wafer and Fasteners for Use in Electronic Theft Detection System," the disclosure of which is incorporated herein by reference. The target wafer disclosed in the Weiner patent is formed as a flat plastic disc with a central hub-like projection and a concentric annular ridge that surrounds and is spaced from the projection. A tack-like fastener, which includes a domed or crowned head and a pointed shank, is releasably attached to the wafer by inserting the shank into a shank-receiving bore formed in the central projection. A gripping or locking device in the wafer holds the fastener securely in place until it is released using a specially designed releasing device.
The geometry of the dome-headed fastener and that of the wafer are such that the attachment of the fastener to the wafer is intended to be highly tamper-resistant. When the fastener is in its secured position, the dome-head cannot be easily gripped by conventional gripping tools, and the concentric ridge surrounding the fastener head generally limits the use a lever or other prying tool to pry the secured fastener from the wafer.
Theft prevention systems of the type disclosed in the Weiner patent have generally been effective for their intended purpose. However, determined thieves have developed compact tools which use the design configuration of the domed-headed fastener and concentric ridge to assist in the removal of fastener. More specifically, thieves have modified conventional screwdrivers by notching the tip of the screwdriver blade and bending the screwdriver blade over at an acute angle to create a miniature pry bar. The notched edge of the blade is held against the rim of the fastener head while the acutely bent portion of the screwdriver blade is positioned on the inwardly facing surface of the concentric ridge. When the distance between the notched tip and the acute bend in the screwdriver blade is properly formed, a substantial prying force can be applied against the fastener. The prying force can be applied to bend the head relative the shank or to lift the fastener relative the wafer to provide enough room for diagonal wire cutters to snip through the shank. Alternately, the prying force can be applied in a successive manner on opposite sides of the fastener head until the shank fractures. Thus, the concentric ridge formed on the wafer to deter tampering is used as a base or fulcrum to facilitate unauthorized removal of the fastener.
Since wafers and fasteners of the type disclosed in the Weiner patent are widely used in the retail apparel industry, any thief-developed tools that compromise the physical integrity of the secured fastener diminish the usefulness of the devices in deterring theft.